Method and system for I/Q mismatch calibration and compensation for wideband communication receivers

ABSTRACT

Methods and systems for I/Q mismatch calibration and compensation for wideband communication receivers may comprise receiving a plurality of radio frequency (RF) channels, downconverting the received plurality of received RF channels to baseband frequencies, determining and removing average in-phase (I) and quadrature (Q) gain and phase mismatch of the downconverted channels, determining a residual phase and amplitude tilt of the downconverted channels with removed average I and Q gain and phase mismatch, and compensating for said residual phase and amplitude tilt I and Q gain and phase mismatch of the downconverted channels. The determined phase tilt may be compensated utilizing a phase tilt correction filter, which may comprise one or more all-pass filters. The average I and Q gain and phase mismatch may be determined utilizing a blind source separation (BSS) estimation algorithm.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application makes reference to and claims priority to U.S.Provisional Application Ser. No. 61/481,661 filed on May 2, 2011, whichis hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to data communication. Morespecifically, certain embodiments of the invention relate to a methodand system for I/Q mismatch calibration and compensation for widebandcommunication receivers.

BACKGROUND OF THE INVENTION

Television providers have moved significantly toward cable and satellitetechnology for providing content to users, but terrestrial transmissionstill has significant usage worldwide. Analog television signals arestill utilized in many areas of the world, and are also utilized inportions of digital provider networks.

Receivers introduce undesirable impairments to a signal when the signalis being amplified, filtered or downconverted. For example, directconversion receivers (also referred to as “DCR”, “zero IF receivers”, or“ZIF receivers”) are a very efficient way of implementing a radioreceiver. However these receivers introduce a variety of impairments toa signal which can degrade overall performance of the system. Mostnotably, DC offset and signal image due to imbalances in the complexsignal path, often referred to as “I/Q mismatch,” may corrupt thedownconverted signal. Existing methods for performing DC offsetcancellation (DCOC) and I/Q calibration (IQ cal) can be effective atmitigating these problems. However, for signals which require very highsignal to noise ratio such as analog TV signals, the residual impairmentdue to the limitations of these techniques can still leave visibleartifacts in the analog picture screen.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present invention as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method for I/Q mismatch calibration and compensation forwideband communication receivers, substantially as shown in and/ordescribed in connection with at least one of the figures, as set forthmore completely in the claims.

Various advantages, aspects and novel features of the present invention,as well as details of an illustrated embodiment thereof, will be morefully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary communication device with I/Qmismatch calibration and compensation, in accordance with an embodimentof the invention.

FIG. 2 is a diagram illustrating an exemplary receiver with I/Q mismatchcalibration and compensation, in accordance with an embodiment of theinvention.

FIG. 3 is a diagram illustrating exemplary steps for I/Q mismatchcalibration and compensation, in accordance with an embodiment of theinvention.

FIG. 4 is a diagram illustrating exemplary I/Q mismatch calibration andcompensation circuitry, in accordance with an embodiment of theinvention.

FIG. 5 is a diagram illustrating an exemplary blind source separationalgorithm process, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects of the invention may be found in a method and system forI/Q mismatch calibration and compensation for wideband communicationreceivers. Exemplary aspects of the invention may comprise receiving aplurality of radio frequency (RF) channels, downconverting the receivedplurality of RF channels to baseband frequencies, determining averagein-phase (I) and quadrature (Q) gain and phase mismatch of thedownconverted channels, removing the determined average I and Q gain andphase mismatch, determining a residual phase and amplitude tilt of thedownconverted channels with removed average I and Q gain and phasemismatch, and compensating for the determined residual phase andamplitude tilt. A curvature of gain mismatch may be determined for thedownconverted channels utilizing a blind source separation (BSS)estimation algorithm and a frequency of the down-converted channels maybe shifted in a direction based on the determined curvature. Thedetermined phase tilt may be compensated utilizing a phase tiltcorrection filter, which may comprise one or more all-pass filters. Asignal may be passed through the phase tilt correction filter for thecompensation, wherein the signal comprises a sum of two channels shiftedin frequency based on a determined curvature of the gain mismatch. Theaverage I and Q gain and phase mismatch may be determined utilizing ablind source separation (BSS) estimation algorithm. An estimatingfunction of the BSS algorithm may be averaged over a number of samplesand a separating matrix may be updated based on the averaging. Thereceiver may comprise a direct conversion receiver.

FIG. 1 is a diagram of an exemplary communication device with I/Qmismatch calibration and compensation, in accordance with an embodimentof the invention. Referring to FIG. 1, there is shown the receiver 101comprising a radio frequency (RF) module 105, an RF-to-basebandconversion module 107, an in-phase and quadrature (I/Q) calibration andcompensation module 109, a baseband module 111, a processor 113, and amemory 115.

The RF module 105 may comprise one or more RF receive (Rx) and transmit(Tx) paths for receiving signals from a satellite system, cable TVhead-end, and/or terrestrial TV antennas, for example. The RF module 105may comprise impedance matching elements, LNAs, power amplifiers,variable gain amplifiers, and filters, for example. The RF module 105may thus be operable to receive, amplify, and filter RF signals beforecommunicating them to the RF-to-baseband module 107.

The RF-to-baseband module 107 may comprise mixers and local oscillatorsthat may be operable to receive RF signals and down-convert them tobaseband signals for further processing by the baseband module 111. TheRF-to-baseband module 107 may comprise in-phase and quadrature mixersfor use with polar signals, for example. The RF module 105 and theRF-to-baseband module 107 may comprise a wide bandwidth such thatmultiple channels may be received and down-converted to baseband.

The I/Q calibration and compensation module 109 may comprise circuitryoperable to measure I and Q mismatch between RF paths in the RF module105 and the RF-to-baseband module 107.

The baseband module 111 may comprise circuitry operable to processreceived baseband signals. For example, the baseband module 111 maycomprise filters and amplifiers for further processing of the selectedbaseband signals. In addition, the baseband module 111 may comprise oneor more analog-to-digital converters (ADCs) to convert the receivedanalog signals to digital signals for processing by the processor 113.

The processor 113 may comprise a general purpose processor, such as areduced instruction set computing (RISC) processor, for example, thatmay be operable to control the functions of the receiver 101. Forexample, the processor 113 may configure the frequency control module109 to shift impairments between desired signals so as to reduce oreliminate interference. Additionally, the processor 113 may demodulatebaseband signals received from the baseband module 111.

The memory 115 may comprise a programmable memory module that may beoperable to store software and data, for example, for the operation ofthe receiver 101. Furthermore, the memory 115 may store the frequencyconfigurations performed by the frequency control module 109.

Receivers introduce undesirable impairments to a signal when the signalis being amplified, filtered or downconverted. For example, directconversion receivers, which may also be referred to as “DCR”, “zero IFreceivers”, or “ZIF receivers”, are a very efficient way of implementinga radio receiver. However, they introduce a variety of impairments to asignal which can degrade overall performance of the system.

Most notably, signal images due to imbalances in the complex signal path(often referred to as I/Q mismatch) may corrupt the downconvertedsignal. In a typical RF and analog implementation, the I path and the Qpath have gain and phase mismatches. The phase difference between localoscillator (LO) signals for I and Q mixing may deviate from 90 degrees,mixers may have gain imbalance, and filter pole locations may vary dueto limited circuit-level matching. In addition, the mismatch betweenfilters may result in frequency-dependent gain and phase mismatches. Assuch, a wideband input signal may experience gain and phase mismatchwith frequency dependency.

Due to I/Q gain and phase mismatch, an image of a channel falls into itsimage channel. In the channel example shown by RF IN in FIG. 1, theimage of channel +1 falls into channel −1 and the image of channel −1falls into channel +1. Without proper rejection of the images,signal-to-noise ratio and thus system performance may degrade. A strongfrequency dependence may make the problem even more challenging.Therefore, calibration and compensation for frequency-dependent I/Qmismatch in a wideband receiver may greatly improve performance.

In an exemplary embodiment, I and Q gain and phase mismatch may becalibrated and compensated for in the receiver 101 utilizing blindsource separation (BSS) algorithms on a selected channel and its image.In this scenario, the frequency dependent I/Q mismatch may be calibratedand a compensation process may be executed by the I/Q calibration andcompensation module 109 to mitigate the mismatch.

FIG. 2 is a diagram illustrating an exemplary receiver with I/Q mismatchcalibration and compensation, in accordance with an embodiment of theinvention. Referring to FIG. 2, there is shown a receiver 200 comprisinga low noise amplifier (LNA) 201, an in-phase (I) path 210, a quadrature(Q) path 220, and a processing module 211. The I path 210 and the Q path220 may comprise I and Q mixers 203A and 203B, low-pass filters 205A and205B, local oscillator signals LO_I and LO_Q, gain stages 207A and 207B,analog-to-digital converters (ADCs) 209A and 209B. There is also shownan input signal RF IN comprising the exemplary received channelscentered around LO frequency f_(LO) shown in the inset above the signalRF IN and the LNA 201, and output channels 213.

The LNA 201 may be operable to provide amplification to the signal RF Inwith the amplified signal being communicated to the mixers 203A and203B. The signal RF In may be down-converted to in-phase and quadraturesignals in the I path and Q path in the receiver 200 utilizing the 90degree phase difference LO signals LO_I and LO_Q.

The mixers 203A and 203B may comprise circuitry that is operable togenerate output signals at frequencies that are the sum and thedifference between the input RF signal RF In and the local oscillatorsignal, which comprises either LO_I or LO_Q. The frequency of LO_I andLO_Q may be configured such that it is centered within the desiredchannels. The local oscillators signals LO_I And LO_Q may be generatedby voltage-controlled oscillators in a phase-locked loop, for example,where the frequency of oscillation may be configured by a controlvoltage.

The low-pass filters 205A and 205B may comprise circuitry that isoperable to attenuate signals above a corner frequency and allow signalsbelow the corner frequency to pass. In this manner, sum frequencysignals from the mixers 203A and 203B may be filtered while differencefrequency signals may be allowed to pass through to the gain modules207A and 207B.

The gain modules 207A and 207B may comprise amplifiers for amplifyingthe down-converted and filtered signals. The gain modules 207A and 207Bmay comprise configurable gain levels, and may be controlled by theprocessing module 211, for example.

The ADCs 209A and 209B may comprise circuitry that is operable toconvert analog input signals to digital output signals. Accordingly, theADCs 209A and 209B may receive baseband analog signals from the gainmodules 207A and 207B and may generate digital signals to becommunicated to the processing module 211.

The processing module 211 may comprise a processor similar to theprocessor 113, for example, described with respect to FIG. 1.Accordingly, the processing module 213 may be operable to control thefunctions of the receiver 200 and may process received baseband signalsto demodulate, deinterlace, and/or perform other processing techniquesto the data. Furthermore, the processing module 211 may perform I/Qmismatch calibration and compensation.

In an exemplary scenario, the I/Q calibration and compensation processperformed by the processing module 211 may calibrate without acalibration signal, and may calibrate the I/Q mismatch utilizing thesignal being received by the system under normal operation. Furthermore,the calibration and compensation may be performed entirely in thedigital domain, thereby inducing no overhead in the RF/analog domain.The digital signal processing required for calibration and compensationmay be performed over a pair of channels that are image channels of eachother, i.e., channel k and −k, not over the entire wideband signal. Thisincreases power efficiency thereby supporting large capture bandwidthand more scalability to support a large number of channels.

To calibrate and compensate for frequency dependence of any I/Qmismatch, the process may approximate the frequency dependency over achannel bandwidth as linear. As such, the I/Q gain and phase mismatchesmay be represented as a sum of an average term and a linearly varyingterm (i.e., an amplitude tilt for gain mismatch and a phase tilt forphase mismatch), which makes the calibration process more tractable andleads to a more efficient implementation.

The calibration process may be based on blind source separation (BSS)algorithms to estimate the gain and phase mismatch averaged over acertain bandwidth. The amplitude tilt and the phase tilt may be detectedby first measuring the average gain and phase mismatch over twosub-bands, one at the lower side of the channel bandwidth and the otherat the upper side. The tilts may then be calculated from this two-pointmeasurement.

The iterative process may compensate for the amplitude and phase tiltsvia an efficient implementation as described further with respect toFIGS. 3 and 4. The BSS method estimates the complex couplingcoefficients between the two channels—the desired and image channels.This coupling coefficient may be reduced in an iterative process.Further, the process may enable independent compensation of theamplitude and phase tilts.

FIG. 3 is a diagram illustrating exemplary steps for I/Q mismatchcalibration and compensation, in accordance with an embodiment of theinvention. Referring to FIG. 3, there is shown steps 1-8 in I/Qcalibration and compensation in the receiver 100.

In step 1, a received digital wideband signal may be down-converted,filtered and down-sampled to generate the digital baseband data samplesfor a channel k and its image channel −k. In step 2, the average gainand phase mismatch may be estimated over the channel bandwidth. Aneffective estimation based on blind source separation (BSS) may beutilized with two features for improved I/Q mismatch calibration andcompensation. First, the initial conditions of the separating matrix, B,as described further with respect to FIG. 5, may be configuredappropriately to improve convergence speed. Additionally, the estimatingfunction, H, also described further with respect to FIG. 5, may beaveraged over a number of samples and update the separating matrix Busing the average estimating function H. This tends to smooth theconvergence and reduces the computation complexity since the rate ofupdating matrix B is much lower.

For example, in setting the initial condition of the BSS algorithm,variance of the received signal in channel k and −k may be estimated.The variance information may be used to determine if I/Q mismatchcalibration and compensation is necessary. The variance information mayalso be used to determine which image coupling coefficients may be usedfor tilt estimation, given the asymmetric image rejection performancewhen the signal power of channel k and −k is not equal.

In an exemplary scenario, the coupling coefficient based on thecorrelation between signals in the +k and −k channels is zero when thereis no I/Q mismatch, and non-zero in the presence of mismatch. Thus, thecomplex number coupling coefficient may be utilized to determine thephase and amplitude mismatch, and therefore minimized by adjusting gain,LO phase, and/or filter frequency response in the receiver.

In step 3, the curvature of the gain mismatch may be determined for eachchannel, which may be accomplished using average I/Q mismatch data foreach channel.

In step 4, the phase and amplitude tilt may be detected. To do this, thechannels k and −k may be shifted in the direction determined bycurvature and then summed to form a signal, which may be high-passfiltered and low-pass filtered to pick up two sub-band signals, one atthe lower side of the channel bandwidth and the other at the upper side.Then the average gain and phase mismatch may be measured over these twosubbands. The tilts may then be calculated from this two-pointmeasurement.

In step 5, the phase tilt may be corrected by passing the summed signalthrough a phase tilt correction filter, which may comprise all-passfilters. One advantage of all-pass filters is that this enablesindependent control/correction of the phase tilt and amplitude tilt.

In step 6, the amplitude tilt may be corrected by passing the summedsignal through an amplitude tilt correction filter. Steps 2-6 may besubsequently iterated until convergence or process termination occurs.Convergence may be reached when the average coupling coefficient betweenthe 2^(nd) or higher order correlation statistics between the channelsapproaches zero or falls below an acceptable threshold. Once convergencehas been reached, the desired sideband may be converted to baseband instep 8.

The above I/Q mismatch calibration and compensation process may beaccomplished using the circuitry illustrated in FIG. 4. The calibrationprocess and correction of the frequency-dependent I/Q mismatch may beembedded in the receiver, and thus not require separate calibrationpaths. After calibration, compensation of the frequency-dependent I/Qmismatch follows by simply applying the average I/Q imbalance, amplitudetilt and phase tilt at the convergence point of the calibration process.

FIG. 4 is a diagram illustrating exemplary I/Q mismatch calibration andcompensation circuitry, in accordance with an embodiment of theinvention. Referring to FIG. 4, there is shown a receiver 400 with I/Qmismatch calibration and compensation comprising a mixer 401, a low-passfilter 403, a BSS module 405, mixers 407A and 407B, a summer 409,low-pass filters 411, 413, and 415, a high-pass filter 417, a tiltestimator module 419, and an output mixer 421. The components in FIG. 4may operate exclusively in the digital domain, or with some in analogand some in digital. Furthermore, the steps in the I/Q mismatchcalibration and compensation process described with respect to FIG. 3may correspond to the numbers 1-8 shown in FIG. 4.

The mixer 401 may be operable to down-convert received RF signals tobaseband frequencies, and as such may be substantially similar to themixers 203A and 203B. The low-pass filter 403 may be operable to filterout signals at a frequency above a corner frequency and allow lowerfrequency signals to pass to the BSS module 405.

The BSS module 405 may comprise circuitry, logic, and/or code that isoperable to estimate the average gain and phase mismatch over thebandwidth of the received channel. The BSS module 405 may also beoperable to determine the curvature of the gain mismatch for eachchannel using average I/Q mismatch data for each received channel.Accordingly, the BSS module 405 may be operable to control the gain andphase characteristics of the mixers 407A and 407B to compensate for Iand Q mismatch in the receiver. The BSS module 405 may be operable todown-sample received digital channel signals.

The mixers 407A and 407B may be operable to down-convert receivedsignals to a lower baseband frequency. The mixers 407A and 407B maydown-convert upper and lower frequencies within a channel to enable thedetermination of I/Q phase and amplitude tilt within the channel.

The summer 409 may be operable to sum the signals down-converted by themixers 407A and 407B to generate a signal, which may be utilized todetermine the phase and amplitude tilts. This may be accomplished byshifting the +k and −k channels in the direction determined by thecurvature before summing them.

The signals may then be filtered by the low-pass filter 415 andhigh-pass filter 417, to generate two sub-band signals, one at the lowerside of the channel and the other at the higher side. The average gainand phase mismatch may be measured in these sub-bands by the tiltestimator module 419, which may be utilized to calculate the gain andphase tilt.

The determined tilt values may be utilized to compensate for the gainand tilt by the phase tile correction filter 411 and the amplitudecorrection filter 413. The tilt estimator 419 may comprise separatecircuitry, or may be integrated in the processor module 213, forexample.

The curvature and phase and amplitude tilt control loops may be iterateduntil convergence, upon which the desired sideband may be converted tobaseband by the mixer 421.

FIG. 5 is a diagram illustrating an exemplary blind source separationalgorithm process, in accordance with an embodiment of the invention.Referring to FIG. 5, there is shown a BSS process 500 comprising amixing matrix A 501 and a separating matrix B 503. There is also shownsource signal S 505, signal X 507, and estimated signals Y 509.

Referring to FIG. 5, it is shown that the estimated signals y 509 may bedescribed by y_(t)=B_(t)*x_(t) where B_(t) is the separating matrix B503. The BSS algorithm predicts a subsequent separating matrix, B_(t+1),as B_(t)−λ_(t)*H(y_(t))*B_(t), where H(y) is defined byH(y)=f(y)*g^(H)(y)−I, with I being an identity matrix. Furthermore,f_(i)(y_(i))=y_(i)*|y_(i)|², andg_(i)(y_(i))=sign(Re{y_(i)})+j*sign(Im{y_(i)}), where i is between 1 and2, inclusive.

Utilizing the above relations, the BSS module 405 may determine averagegain and phase mismatch for I and Q signals and remove the averages,with the resulting signal communicated to circuitry for furtherprocessing and tilt estimation, as shown in FIG. 4.

In an embodiment of the invention, a method and system may comprisereceiving a plurality of radio frequency (RF) channels −3, −2, −1, +1,+2, +3, downconverting the received plurality of received RF channels−3, −2, −1, +1, +2, +3 to baseband frequencies, determining averagein-phase (I) and quadrature (Q) gain and phase mismatch of thedownconverted channels, removing the determined average I and Q gain andphase mismatch, determining a residual phase and amplitude tilt 419 ofthe downconverted channels with removed average I and Q gain and phasemismatch, and compensating for the residual I and Q gain 413 and phase411 tilt of the downconverted channels utilizing the determined phaseand amplitude tilt 419.

A curvature of gain mismatch may be determined for the downconvertedchannels utilizing a blind source separation (BSS) estimation algorithm405 and a frequency of the down-converted channels may be shifted in adirection based on the determined curvature. The determined phase tiltmay be compensated utilizing a phase tilt correction filter 411, whichmay comprise one or more all-pass filters. A signal may be passedthrough the phase tilt correction filter 411 for the compensation,wherein the signal comprises a sum of two channels shifted in frequencybased on a determined curvature of the gain mismatch. The average I andQ gain and phase mismatch may be determined utilizing a blind sourceseparation (BSS) estimation algorithm. An estimating function of the BSSalgorithm may be averaged over a number of samples and a separatingmatrix may be updated based on the averaging. The receiver 400 maycomprise a direct conversion receiver.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for I/Omismatch calibration and compensation for wideband communicationreceivers.

Accordingly, aspects of the invention may be realized in hardware,software, firmware or a combination thereof. The invention may berealized in a centralized fashion in at least one computer system or ina distributed fashion where different elements are spread across severalinterconnected computer systems. Any kind of computer system or otherapparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware, software and firmware may bea general-purpose computer system with a computer program that, whenbeing loaded and executed, controls the computer system such that itcarries out the methods described herein.

One embodiment of the present invention may be implemented as a boardlevel product, as a single chip, application specific integrated circuit(ASIC), or with varying levels integrated on a single chip with otherportions of the system as separate components. The degree of integrationof the system will primarily be determined by speed and costconsiderations. Because of the sophisticated nature of modernprocessors, it is possible to utilize a commercially availableprocessor, which may be implemented external to an ASIC implementationof the present system. Alternatively, if the processor is available asan ASIC core or logic block, then the commercially available processormay be implemented as part of an ASIC device with various functionsimplemented as firmware.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext may mean, for example, any expression, in any language, code ornotation, of a set of instructions intended to cause a system having aninformation processing capability to perform a particular functioneither directly or after either or both of the following: a) conversionto another language, code or notation; b) reproduction in a differentmaterial form. However, other meanings of computer program within theunderstanding of those skilled in the art are also contemplated by thepresent invention.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiments disclosed, but that the present inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for wireless communication, the methodcomprising: in a communication device: receiving a plurality of radiofrequency (RF) channels in a receiver of said communication device;downconverting said received plurality of received RF channels tobaseband frequencies; determining average in-phase (I) and quadrature(Q) gain and phase mismatch of said downconverted channels; determininga curvature of gain mismatch for said downconverted channels utilizing ablind source separation (BSS) estimation algorithm; removing saidaverage I and Q gain and phase mismatch of said downconverted channels;determining a residual phase tilt and a residual amplitude tilt of saiddownconverted channels with removed average I and Q gain and phasemismatch; and compensating for said determined residual phase tilt andsaid determined residual amplitude tilt of said downconverted channelswith removed average I and Q gain and phase mismatch, whereincompensating for said determined residual phase tilt comprises passing asignal through a phase tilt correction filter, and wherein said signalcomprises a sum of two channels shifted in frequency based on saiddetermined curvature of said gain mismatch.
 2. The method according toclaim 1, comprising shifting a frequency of said down-converted channelsin a direction based on said determined curvature.
 3. The methodaccording to claim 1, wherein said phase tilt correction filtercomprises one or more all-pass filters.
 4. The method according to claim1, comprising determining said average I and Q gain and phase mismatchutilizing said blind source separation (BSS) estimation algorithm. 5.The method according to claim 4, comprising averaging an estimatingfunction of said BSS algorithm over a number of samples and updating aseparating matrix based on said averaging.
 6. The method according toclaim 1, wherein said receiver is a direct conversion receiver.
 7. Asystem for wireless communication, the system comprising: one or morecircuits for use in a communication device, said one or more circuitsbeing operable to: receive a plurality of radio frequency (RF) channelsin a receiver of said communication device; downconvert said receivedplurality of received RF channels to baseband frequencies; determineaverage in-phase (I) and quadrature (Q) gain and phase mismatch of saiddownconverted channels; determine a curvature of gain mismatch for saiddownconverted channels utilizing a blind source separation (BSS)estimation algorithm; remove said average I and Q gain and phasemismatch of said downconverted channels; determine a residual phase tiltand a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; and compensate for saiddetermined residual phase tilt and said determined residual amplitudetilt of said downconverted channels with removed average I and Q gainand phase mismatch, wherein said compensation for said determinedresidual phase tilt comprises passing a signal through a phase tiltcorrection filter, and wherein said signal comprises a sum of twochannels shifted in frequency based on said determined curvature of saidgain mismatch.
 8. The system according to claim 7, wherein said one ormore circuits are operable to shift a frequency of said down-convertedchannels in a direction based on said determined curvature.
 9. Thesystem according to claim 7, wherein said phase tilt correction filtercomprises one or more all-pass filters.
 10. The system according toclaim 7, wherein said one or more circuits are operable to determinesaid average I and Q gain and phase mismatch utilizing said blind sourceseparation (BSS) estimation algorithm.
 11. The system according to claim10, wherein said one or more circuits are operable to average anestimating function of said BSS algorithm over a number of samples andupdating a separating matrix based on said averaging.
 12. A method forwireless communication, the method comprising: in a communicationdevice: receiving a plurality of radio frequency (RF) channels in areceiver of said communication device; downconverting said receivedplurality of received RF channels to baseband frequencies; determiningaverage in-phase (I) and quadrature (Q) gain and phase mismatch of saiddownconverted channels; removing said average I and Q gain and phasemismatch of said downconverted channels; determining a residual phasetilt and a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; compensating for saiddetermined residual phase tilt utilizing a phase tilt correction filter;passing a signal through said phase tilt correction filter for saidcompensation, wherein said signal comprises a sum of two channelsshifted in frequency based on a determined curvature of said gainmismatch; and compensating for said determined residual phase tilt andsaid determined residual amplitude tilt of said downconverted channelswith removed average I and Q gain and phase mismatch.
 13. The methodaccording to claim 12, comprising determining a curvature of gainmismatch for said downconverted channels.
 14. The method according toclaim 13, comprising shifting a frequency of said down-convertedchannels in a direction based on said determined curvature.
 15. Themethod according to claim 12, comprising compensating for saiddetermined residual phase tilt utilizing a phase tilt correction filter.16. The method according to claim 12, wherein said phase tilt correctionfilter comprises one or more all-pass filters.
 17. The method accordingto claim 12, comprising determining said average I and Q gain and phasemismatch utilizing a blind source separation (BSS) estimation algorithm.18. The method according to claim 17, comprising averaging an estimatingfunction of said BSS algorithm over a number of samples and updating aseparating matrix based on said averaging.
 19. The method according toclaim 12, wherein said receiver is a direct conversion receiver.
 20. Asystem for wireless communication, the system comprising: one or morecircuits for use in a communication device, said one or more circuitsbeing operable to: receive a plurality of radio frequency (RF) channelsin a receiver of said communication device; downconvert said receivedplurality of received RF channels to baseband frequencies; determineaverage in-phase (I) and quadrature (Q) gain and phase mismatch of saiddownconverted channels; remove said average I and Q gain and phasemismatch of said downconverted channels; determine a residual phase tiltand a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; compensate for saiddetermined residual phase tilt utilizing a phase tilt correction filter;pass a signal through said phase tilt correction filter for saidcompensation, wherein said signal comprises a sum of two channelsshifted in frequency based on a determined curvature of said gainmismatch; and compensate for said determined residual phase tilt andsaid determined residual amplitude tilt of said downconverted channelswith removed average I and Q gain and phase mismatch.
 21. The systemaccording to claim 20, wherein said one or more circuits is operable todetermine a curvature of gain mismatch for said downconverted channels.22. The system according to claim 21, wherein said one or more circuitsare operable to shift a frequency of said down-converted channels in adirection based on said determined curvature.
 23. The system accordingto claim 20, wherein said one or more circuits are operable tocompensate for said determined residual phase tilt utilizing a phasetilt correction filter.
 24. The system according to claim 23, whereinsaid phase tilt correction filter comprises one or more all-passfilters.
 25. The system according to claim 20, wherein said one or morecircuits are operable to determine said average I and Q gain and phasemismatch utilizing a blind source separation (BSS) estimation algorithm.26. The system according to claim 25, wherein said one or more circuitsare operable to average an estimating function of said BSS algorithmover a number of samples and updating a separating matrix based on saidaveraging.
 27. A method for wireless communication, the methodcomprising: in a communication device: receiving a plurality of radiofrequency (RF) channels in a receiver of said communication device;downconverting said received plurality of received RF channels tobaseband frequencies; determining average in-phase (I) and quadrature(Q) gain and phase mismatch of said downconverted channels utilizing ablind source separation (BSS) estimation algorithm; removing saidaverage I and Q gain and phase mismatch of said downconverted channels;determining a residual phase tilt and a residual amplitude tilt of saiddownconverted channels with removed average I and Q gain and phasemismatch; and compensating for said determined residual phase tilt andsaid determined residual amplitude tilt of said downconverted channelswith removed average I and Q gain and phase mismatch, wherein saidcompensating for said determined residual phase tilt utilizes a phasetilt correction filter.
 28. The method according to claim 27, comprisingdetermining a curvature of gain mismatch for said downconvertedchannels.
 29. The method according to claim 28, comprising shifting afrequency of said down-converted channels in a direction based on saiddetermined curvature.
 30. The method according to claim 27, wherein saidphase tilt correction filter comprises one or more all-pass filters. 31.The method according to claim 27, wherein said receiver is a directconversion receiver.
 32. A method for wireless communication, the methodcomprising: in a communication device: receiving a plurality of radiofrequency (RF) channels in a receiver of said communication device;downconverting said received plurality of received RF channels tobaseband frequencies; determining average in-phase (I) and quadrature(Q) gain and phase mismatch of said downconverted channels utilizing ablind source separation (BSS) estimation algorithm; averaging anestimating function of said BSS algorithm over a number of samples andupdating a separating matrix based on said averaging; removing saidaverage I and Q gain and phase mismatch of said downconverted channels;determining a residual phase tilt and a residual amplitude tilt of saiddownconverted channels with removed average I and Q gain and phasemismatch; and compensating for said determined residual phase tilt andsaid determined residual amplitude tilt of said downconverted channelswith removed average I and Q gain and phase mismatch.
 33. The methodaccording to claim 32, comprising determining a curvature of gainmismatch for said downconverted channels.
 34. The method according toclaim 33, comprising shifting a frequency of said down-convertedchannels in a direction based on said determined curvature.
 35. Themethod according to claim 32, comprising compensating for saiddetermined residual phase tilt utilizing a phase tilt correction filter.36. The method according to claim 35, wherein said phase tilt correctionfilter comprises one or more all-pass filters.
 37. The method accordingto claim 32, wherein said receiver is a direct conversion receiver. 38.A system for wireless communication, the system comprising: one or morecircuits for use in a communication device, said one or more circuitsbeing operable to: receive a plurality of radio frequency (RF) channelsin a receiver of said communication device; downconvert said receivedplurality of received RF channels to baseband frequencies; determineaverage in-phase (I) and quadrature (Q) gain and phase mismatch of saiddownconverted channels utilizing a blind source separation (BSS)estimation algorithm; average an estimating function of said BSSalgorithm over a number of samples and updating a separating matrixbased on said averaging; remove said average I and Q gain and phasemismatch of said downconverted channels; determine a residual phase tiltand a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; and compensate for saiddetermined residual phase tilt and said determined residual amplitudetilt of said downconverted channels with removed average I and Q gainand phase mismatch.
 39. The system according to claim 38, wherein saidone or more circuits is operable to determine a curvature of gainmismatch for said downconverted channels.
 40. The system according toclaim 39, wherein said one or more circuits are operable to shift afrequency of said down-converted channels in a direction based on saiddetermined curvature.
 41. The system according to claim 38, wherein saidone or more circuits are operable to compensate for said determinedresidual phase tilt utilizing a phase tilt correction filter.
 42. Thesystem according to claim 41, wherein said phase tilt correction filtercomprises one or more all-pass filters.
 43. A method for wirelesscommunication, the method comprising: in a communication device:receiving a plurality of radio frequency (RF) channels in a receiver ofsaid communication device; downconverting said received plurality ofreceived RF channels to baseband frequencies; determining averagein-phase (I) and quadrature (Q) gain and phase mismatch of saiddownconverted channels utilizing a blind source separation (BSS)estimation algorithm; determining a curvature of gain mismatch for saiddownconverted channels utilizing a blind source separation (BSS)estimation algorithm; removing said average I and Q gain and phasemismatch of said downconverted channels; determining a residual phasetilt and a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; and compensating forsaid determined residual phase tilt and said determined residualamplitude tilt of said downconverted channels with removed average I andQ gain and phase mismatch.
 44. The method according to claim 43,comprising shifting a frequency of said down-converted channels in adirection based on said determined curvature.
 45. The method accordingto claim 43, comprising compensating for said determined residual phasetilt utilizing a phase tilt correction filter.
 46. The method accordingto claim 45, wherein said phase tilt correction filter comprises one ormore all-pass filters.
 47. The method according to claim 43, comprisingaveraging an estimating function of said BSS algorithm over a number ofsamples and updating a separating matrix based on said averaging. 48.The method according to claim 43, wherein said receiver is a directconversion receiver.
 49. A system for wireless communication, the systemcomprising one or more circuits for use in a communication device, saidone or more circuits being operable to: receive a plurality of radiofrequency (RF) channels in a receiver of said communication device;downconvert said received plurality of received RF channels to basebandfrequencies; determine average in-phase (I) and quadrature (Q) gain andphase mismatch of said downconverted channels; determine a curvature ofgain mismatch for said downconverted channels utilizing a blind sourceseparation (BSS) estimation algorithm; remove said average I and Q gainand phase mismatch of said downconverted channels utilizing a blindsource separation (BSS) estimation algorithm; determine a residual phasetilt and a residual amplitude tilt of said downconverted channels withremoved average I and Q gain and phase mismatch; and compensate for saiddetermined residual phase tilt and said residual amplitude tilt of saiddownconverted channels with removed average I and Q gain and phasemismatch.
 50. The system according to claim 49, wherein said one or morecircuits are operable to shift a frequency of said down-convertedchannels in a direction based on said determined curvature.
 51. Thesystem according to claim 49, wherein said one or more circuits areoperable to compensate for said determined residual phase tilt utilizinga phase tilt correction filter.
 52. The system according to claim 51,wherein said phase tilt correction filter comprises one or more all-passfilters.
 53. The system according to claim 49, wherein said one or morecircuits are operable to average an estimating function of said BSSalgorithm over a number of samples and updating a separating matrixbased on said averaging.